Amyloid β protein agglutination-controlling factor

ABSTRACT

The present invention provides: proteins suppressing or promoting the aggregation or deposition of amyloid-β protein; polynucleotides encoding the proteins; a method for screening a compound suppressing or promoting the aggregation or deposition of amyloid-β protein; and therapeutic agents for treating or preventing Alzheimer&#39;s diseases comprising a compound that regulates the activity of a protein suppressing or promoting the aggregation or deposition of amyloid-β protein.

This application claims the benefit of Provisional Application No. 60/159,586 filed Oct. 18, 1999.

TECHNICAL FIELD

The present invention relates to proteins that suppress or promote the aggregation or deposition of amyloid-β protein (also referred to as “Aβ” hereinafter), polynucleotides encoding the proteins, a method for preparing the proteins using the polynucleotides, an expression system for producing the proteins, and a method of screening for a compound that suppresses or promotes the aggregation of amyloid-β protein using the expression system. The present invention also relates to a method for preventing and treating Alzheimer's disease using proteins obtained by the method above, or a compound obtained by the screening method.

BACKGROUND ART

Alzheimer's disease is a disorder associated with cognitive dysfunctions, and is characterized by a loss of nerve cells and emergence of a large number of senile plaques and neurofibrillary tangles. Senile plaques are detected at the earliest stage of development of this disease. These plaques are highly specific to this disease since they are not found in other neurodegenerative disorders. Amyloid-β protein (Aβ) is the major constituent of senile plaques and forms amyloid fibrils having a β-sheet structure. Aβ is a polypeptide comprising approximately 40 amino acid residues and has a molecular weight of 4,000 Da. It easily aggregates to form fibrils and becomes insoluble. The major molecular species of this protein are Aβ40, which ends with valine at amino acid residue 40, and Aβ42, the longer form of Aβ having two additional residues. Although Aβis usually degraded and never accumulates in the brain, the degrading capacity decreases with aging, causing an accumulation of Aβ. This triggers neuronal dysfunction and cell death, ultimately resulting in dementia and Alzheimer's disease. Through various genetic analyses and molecular biological and neuropharmacological studies, “amyloid hypothesis” has been proposed as a cause of the pathogenesis of Alzheimer's disease.

DISCLOSURE OF THE INVENTION

An objective of the present invention is to provide proteins that suppress or promote aggregation or deposition of amyloid-β protein, and polynucleotides encoding these proteins. A further objective of the present invention is to provide a method for treating Alzheimer's disease by discovering a method or substance that suppressesor promotes aggregation or deposition of amyloid-β protein.

To achieve the above objectives, the present inventors conducted extensive studies and finally discovered polynucleotides encoding secretory or membrane-bound forms of proteins that suppress or promote the aggregation or deposition of amyloid-β protein, and hence completed the present invention.

Thus, the present invention relates to:

-   [1] a polynucleotide encoding a protein that suppresses or promotes     the aggregation or deposition of amyloid-β protein, wherein the     polynucleotide is selected from the group consisting of:     -   (a) a polynucleotide that comprises a nucleotide sequence as set         forth in SEQ ID NO: 1, 3, 5, 7 or 9,     -   (b) a polynucleotide that encodes a protein having a amino acid         sequence as set forth in SEQ ID NO: 2, 4, 6, 8 or 10,     -   (c) a polynucleotide that encodes a protein comprising an amino         acid sequence in which one or several amino acids of the amino         acid sequence of SEQ ID NO. 2, 4, 6, 8 or 10, have been         substituted, deleted, inserted and/or added,     -   (d) a polynucleotide that hybridizes under stringent conditions         to a polynucleotide comprising a nucleotide sequence as set         forth in SEQ ID NO. 1, 3, 5, 7 or 9; or,     -   (e) a polynucleotide that shows at least (i) 60%, (ii)70%, (iii)         80%, (iv) 90%, or (v) 95% homology to a nucleotide sequence as         set forth in SEQ ID NO. 1, 3, 5, 7 or 9; -   [2] a polynucleotide encoding a partial peptide of the protein     encoded by a polynucleotide according to [1]; -   [3] a peptide or protein encoded by a polynucleotide according to     [1] or [2]; -   [4] a protein that suppresses or promotes the aggregation of     amyloid-β protein, wherein said protein is encoded by a     polynucleotide that, from a molecular evolutionary aspect,     originated from the same gene from which a polynucleotide according     to [1] originated from; -   [5] a vector comprising a polynucleotide according to [1] or [2]; -   [6] a transfectant harboring a polynucleotide according to [1] or     [2] or the vector according to [5]; -   [7] a method for producing the peptide or protein according to [3],     wherein said method comprises the steps of: culturing the     transfectant according to [6], and recovering the expression     product; -   [8] a polynucleotide comprising a polynucleotide according to [1 or     [2] or a nucleotide sequence complementary to the complementary     strand of the polynucleotide according to [1] or [2], wherein said     polynucleotide comprises at least 15 nucleotides; -   [9] an antibody against the peptide or protein according to (3]; -   [10] an immunological assay comprising the step of: monitoring an     immunological reaction between the peptide or protein according to     [3] and the antibody according to [9]; -   [11] a method of screening for a compound that regulates the     activity of a protein encoded by a polynucleotide according to [1],     wherein said method comprises the following steps of:     -   contacting a candidate compound with a protein encoded by a         polynucleotide according to [1], or with a cell expressing said         protein, in the presence of amyloid-β protein, and,     -   selecting a the candidate compound that regulates the         aggregation or deposition of amyloid-β protein; -   [12] a method of screening for a compound that regulates expression     of a protein encoded by a polynucleotide according to [1], wherein     said method comprises the following steps of:     -   (1) contacting a candidate compound with a cell, wherein a         vector has been introduced into said cell, said vector         comprising:         -   an expression regulatory region of a gene comprising a             nucleotide sequence selected from the group consisting of             SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, and             SEQ ID NO. 9, and, a reporter gene operably linked             downstream of the expression regulatory region,     -   (2) measuring the activity of the reporter gene, and,     -   (3) selecting the candidate compound that increases or decreases         the reporter activity measured instep (b) when compared to the         control; -   [13] a pharmaceutical agent comprising a compound obtained by the     method according to [11] or [12]; -   [14] a pharmaceutical agent comprising the peptide or protein     according to [3] or [4]; -   [15] a pharmaceutical agent comprising an antisense polynucleotide     complementary to the protein-coding sequence of a polynucleotide     according to [1]; -   [16] the pharmaceutical agent according to [13] or [14], wherein     said pharmaceutical agent is a preventive or therapeutic agent for     Alzheimer's disease; and, -   [17] a method for detecting Alzheimer's disease, comprising the     following steps of:     -   (1) measuring the expression of a polynucleotide according to     -   (2) comparing the measurement obtained by (1) with that obtained         when the polynucleotide is expressed in healthy subjects; and,     -   (3) linking Alzheimer's disease with said change in expression         of the polynucleotide.

The proteins of the present invention that suppress or promote the aggregation of amyloid-β protein, and the polynucleotides encoding the proteins comprise the whole or part of the sequence shown in SEQ ID NO. 1, 3, 5, 7 or 9.

The polynucleotides of the present invention may include any nucleotide that can encode the proteins of the present invention, such as genomic DNA and chemically-synthesized DNA as well as cDNA, but are not limited thereto. The polynucleotides of the present invention may also include polynucleotides having any nucleotide sequence that is based on the degeneracy of the genetic code, as long as the polynucleotides encode the proteins of the present invention. The polynucleotides encoding the proteins of the present invention may be isolated by conventional methods, such as hybridization using as a probe a polynucleotide sequence shown in SEQ ID NO. 1, 3, 5, 7 or 9, or a partial sequence thereof, or PCR using primers designed based on the information of these sequences.

A protein of the present invention that suppresses or promotes amyloid-β protein aggregation, can be obtained by expressing the protein in a transformant using an expression vector comprising the open reading frame within the sequence shown in, for example, SEQ ID NO. 1, 3, 5, 7 or 9. These expressed proteins may be purified and isolated, using conventional methods, from the culture or cell fraction. Specifically, methods for purification and isolation are, for example, as follows: first, the cells or supernatant is collected using conventional methods, such as filtration and centrifugation, and the cell membranes and/or the cell walls are then treated by sonication and/or with lysozyme to obtain a cell membrane fraction. Subsequently, the cell membrane fraction thus obtained is dissolved in a suitable solution. From the supernatant or the cell membrane fraction, the protein of the invention is isolated and purified according to conventional methods generally used for purification and isolation of a natural or synthetic protein. Examples of methods for isolation or purification include dialysis, gel filtration, affinity chromatography using a monoclonal antibody against the proteins of the present invention or a partial peptide thereof, column chromatography using an appropriate absorbent, high performance liquid chromatography, etc.

Furthermore, the present invention includes polynucleotides encoding proteins functionally equivalent to the proteins described above. As used herein, the term “functionally equivalent” means that the protein of interest has an activity that suppresses or promotes amyloid-β protein aggregation. The activity that suppresses or promotes amyloid-β protein aggregation can be confirmed by using, for example, the methods described in the working examples. Aβ and its fragments are prone to aggregate under particular conditions. Addition of a test compound under such conditions would give rise to Aβ aggregates, if the test compound had a property that promotes aggregation. A fragment comprising the N-terminal amino acid sequence (residues 1-28) of Aβ has been used in experiments of this sort as a partial peptide having Aβ-aggregating activity (Methods in Enzymology Vol. 309, 274-284, 1999). Aβ aggregation can be detected optically, or can be confirmed microscopically after staining with Congo red and such.

One skilled in the art would be able to prepare proteins functionally equivalent to the proteins used in the β-amyloid aggregation tests described in the working examples below, for example, by using a method for introducing mutations into the amino acid sequences of proteins (e.g. site-directed mutagenesis, Current Protocols in Molecular Biology edit. Ausubel et al. (1987) Publish. John Wily & Sons Section 8.1-8.5). Such proteins might occur due to spontaneous mutation of amino acids in nature. The present invention also includes a protein having an amino acid sequence in which one or several amino acid residues are different from those found in a sequence of any one of the proteins identified in the working examples below (SEQ ID NO. 2, 4, 6, 8 or 10, or the amino acid sequence encoded by SEQ ID NO. 1, 3, 5, 7 or 9) due to a substitution, deletion, insertion and/or addition, as long as the protein retains a function equivalent to the proteins identified in the working examples below.

Number or sites of amino acid mutations in the protein are not limited, as long as the protein function is retained. The number (percentage) of mutations is typically 10% or less, preferably 5% or less, and more preferably 1% or less of the total amino acids. Alternatively, the mutation of “several” amino acids as used in the present invention includes the mutation of a “few” amino acids as well. “Few” refers to, for example, five, four, three, two, or one amino acid. Preferably, in view of maintaining protein function, substituting amino acids may have properties similar to the amino acids to be substituted. For example, Ala, Val, Leu, Ile, Pro, Met, Phe, and Trp are all classified into nonpolar amino acids, and they are thought to share common properties. Uncharged amino acids include Gly, Ser, Thr, Cys, Tyr, Asn, and Gln. Acidic amino acids include Asp and Glu, and basic amino acids include Lys, Arg, and His.

Alternatively, a protein functionally equivalent to the protein identified in the working examples below can be isolated using a hybridization or gene amplification technique well known to one skilled in the art. More specifically, using the hybridization technique (Current Protocols in Molecular Biology edit. Ausubel et al. (1987) Publish. John Wily & Sons Section 6.3-6.4), one skilled in the art would routinely be able to isolate a polynucleotide showing a significant homology to any one of the polynucleotide sequences encoding the proteins identified in the working examples below (SEQ ID NO. 1, 3, 5, 7 or 9) by using a polynucleotide sequences, or a portion thereof, and obtain a functionally equivalent protein from the polynucleotide isolated. The present invention includes a protein encoded by a polynucleotide hybridizing to a polynucleotide encoding a protein identified in the working examples below, as long as the proteins are functionally equivalent. A functionally equivalent protein can be isolated from animals including, but not limited to, vertebrates such as humans, mice, rats, rabbits, pigs, and cattle. From these animals, one can isolate genes that originated from molecular-evolutionarily the same gene that encodes a protein of the present invention that suppresses or promotes amyloid β protein aggregation. As used herein, the term “genes that originated from molecular-evolutionarily the same gene” refers to genes that are rationally judged to have evolved from one ancestor gene from which the human gene of the present invention evolved in the course of molecular-evolution. This judgment is based on polynucleotide sequence analysis of the genes or analysis of their physiological roles and such. Such genes maintain a significant nucleotide sequence homology among them.

Stringent hybridization conditions for isolating a polynucleotide encoding a functionally equivalent protein are, typical washing conditions such as “1×SSC, 0.1% SDS, 37° C.”. More stringent conditions are, for example, “0.5×SSC, 0.1% SDS, 42° C.”, and even more stringent conditions are, for example, “0.1×SSC, 0.1% SDS, 65° C.”. The more stringent the hybridization conditions become, the more homologous to the probe sequence the polynucleotide is expected to be. Note that the above combinations of SSC, SDS, and temperature are given only for illustration, and one skilled in the art can achieve the same level of stringency by combining these factors appropriately to determine the hybridization conditions. The factors include those described above, or other factors (e.g. probe concentrations, length of probes, reaction time, etc.).

In general, a protein isolated using such hybridization techniques shows a significant homology in the nucleotide sequence encoding the protein, or in its amino acid sequence, compared to the sequence of a protein of the present invention, shown in SEQ ID NO. 2, 4, 6, 8 or 10, or a protein encoded by the a sequence shown in SEQ ID NO. 1, 3, 5, 7 or 9. “Significant homology” refers to a sequence identity of at least 60% or more, preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and most preferably 95% or more. Sequence homology can be determined using the BLAST 2 search algorithm (Altschul, S. F. et al, 1997, Gapped BLAST and PSI-BLAST: a new generation of protein database search programs, Nucleic Acids Res. 25: 3389-3402).

A gene-amplification technique (PCR) (Current protocols in Molecular Biology edit. Ausubel et al. (1987) Publish. John Wiley & Sons Section 6.1-6.4) can be used to design primers based on a part of any of the polynucleotide sequences identified in the working examples below (SEQ ID NO. 1, 3, 5, 7 or 9), and to isolate a polynucleotide fragment that shows a significant homology to the above polynucleotide sequence or a portion thereof, to obtain a protein functionally equivalent to the protein identified in the working examples.

The present invention also relates to a partial peptide of the proteins of the present invention and to a polynucleotide encoding the partial peptide. A partial peptide of the present invention comprises at least 7 amino acid residues, preferably 9 or more amino acid residues, more preferably 12 or more amino acid residues, even more preferably 15 or more amino acid residues. The partial peptide of the present invention may be produced by, for example, genetic engineering, a well-known technique for peptide synthesis, or cleavage of the proteins of the present invention with an appropriate peptidase.

The present invention also provides expression vectors comprising any one of the polynucleotides mentioned above. Furthermore, the present invention relates to transfectants harboring any of the expression vectors or polypeptides mentioned above, and a method for producing proteins or partial peptides thereof that suppress or promote amyloid-β protein aggregation. Such a method comprises culturing the transfectant and isolating a protein of the present invention from the culture. Moreover, the present invention provides the protein or partial peptide produced by the above method.

When producing polypeptides by means of genetic recombination, the type and extent of glycosylation of a polypeptide of interest would differ depending on the type of host cell. Furthermore, in the method of so-called “secretory production” of polypeptides, it is well known to one skilled in the art that (N— and/or C—) terminal amino acid sequences of precursor peptides expressed in host cells would undergo processing by signal peptidases and such to produce polypeptides having various terminal sequences. Therefore, one skilled in the art would easily understand that such polypeptides are also included in the proteins of the present invention.

The working examples described below illustrates only an example of constructing a vector that functions in mammalian cells as an expression vector. However, since the polynucleotide sequences encoding the proteins of the present invention are disclosed herein, it would be easy for one skilled in the art to construct an expression vector that can express and produce a protein of the present invention when such a vector is introduced into a fungal host cell, such as a yeast, or a prokaryotic host cell. Therefore, the present invention includes expression vectors constructed using any methods known in the art based on the polynucleotide sequences of the present invention.

Microbial cells that can be used for the expression of the polynucleotides encoding the proteins of the present inventions include, for example, prokaryotic bacteria (e.g. Escherichia coli and Bacillus subtilis) and eukaryotic yeasts (e.g. Saccharomyces cerevisiae). Mammalian cells include cultured human cells and cultured animal cells. Moreover, cultured plant cells can be used.

Examples of microorganisms include bacteria of the genus Escherichia (e.g. E. coli HB101 ATCC 33694, E. coli HB101-16 FERM BP-1872, E. coli MM294 ATCC 31446, E. coli DH1 ATCC 33849, etc.) and baker's yeast (e.g. S. cerevisiae AH22 ATCC 38626, etc.). Examples of mammalian cells include HEK293 cells derived from human embryonic kidney cells, mouse L929 cells, Chinese hamster ovary (CHO) cells, etc.

Generally, expression vectors are constructed with, at least, a promoter, an initiation codon, a polynucleotide encoding the amino acid sequence of any of the proteins of the present invention, a termination codon, and a self-replication unit, when prokaryotes, bacteria, particularly E. coli are used as host cells. When eukaryotic cells such as yeast and mammalian cells are used, expression vectors are preferably constructed with, at least, a promoter, an initiation codon, a polynucleotide encoding the amino acid sequence of any of the proteins of the present invention, and a termination codon. Additionally, an enhancer sequence, 5′- and 3′-untranslated regions for the proteins of the present invention, a polyadenylation site, and a self-replication unit may be integrated.

The self-replication unit preferably comprises a selectable marker for transfectants (e.g. resistance to ampicillin). In the case of expression vectors using bacteria as host cells, the term “promoter” means a promoter-operator region containing a promoter, operator, and a Shine-Dalgarno (SD) sequence (e.g. AAGG, etc.). Examples of such promoters include conventional promoter-operator regions (e.g. the lactose operon, PL-promoter, trp-promoter, etc.). An Example of a promoter for expression vectors used in yeast host cells includes the pho5 promoter. Additionally, to facilitate purification, basic amino acids having affinity for chelated metal ions can be added to either end of a protein of the present invention.

When basic amino acids are added, a primer having, at its 5′-end, a nucleotide sequence sequentially coding for desired amino acid residues can be used for PCR to introduce an oligonucleotide at either end of a gene of interest. Histidine, lysine, arginine, and such can be used as basic amino acids.

Examples of promoters used in expression vectors in mammalian cells include the HTLV-LTR promoter, early and late SV40 promoters, CMV promoters, the mouse metallothionein I (MMT) promoter, etc. A preferred example of an initiation codon is the methionine codon (ATG).

A polynucleotide encoding an amino acid sequence of the proteins of the present invention may be obtained by, for example, partial or complete synthesis of nucleotides using a DNA synthesizer. Alternatively, it can be obtained from a human cDNA library by using a probe or primer set that is designed based on a nucleotide sequence as shown in SEQ ID NO. 1, 3, 5, 7 or 9. The genomic DNA encoding the proteins of the present invention can also be prepared by treating genomic DNA according to a conventional method (e.g. digestion with restriction enzymes, dephosphorylation by bacterial alkaline phosphatase, phosphorylation by T4 polynucleotide kinase, and ligation with T4 DNA ligase). Furthermore, the genomic DNA thus obtained can be used to demonstrate the transcriptional initiation site of a gene of the present invention located on the genome. This allows one to specify expression-regulatory regions located upstream of the gene. Regulatory regions, such as promoters and enhancers, which would control expression of the a encoding a protein of the present invention, are useful as target regions for detecting aberrant expression of a protein of the present invention. Regulation of gene expression can be achieved using decoy nucleotide pharmaceuticals that target such regions.

The host cells of the present invention include cells used for functional analysis of the proteins of the present invention and those used for screening inhibitors or enhancers of the functions of the proteins. Introduction of a vector into host cells may be conducted using any of the methods including, for example, calcium phosphate precipitation, electroporation (Current protocols in Molecular Biology edit. Ausubel et al. (1987) Publish. John Wiley & Sons. Section 9.1-9.9), the lipofectamine method, and micro injection. Preparation of the proteins of the present invention from transfectants may be conducted using any of the isolation and purification methods well known to one skilled in the art.

The present invention also provides a polynucleotide comprising at least 15 nucleotides, which is complementary to any of the polynucleotide sequences shown in SEQ ID NO. 1, 3, 5, 7, or 9, or to a complementary strand thereof. As used herein, the term “complementary strand” refers to one strand of a double-stranded polynucleotide that forms base pairs of A:T (A:U) and G:C with the other strand of the polynucleotide. Also, “complementary” is defined as not only sequences that completely match a continuous nucleotide region of at least 15 nucleotides, but also sequences having a homology of at least 70%, preferably 80% or more, more preferably 90% or more, and most preferably 95% or more to that region. Sequence homology can be determined according to the algorithm as described in this description.

Such a polynucleotide can be used as a probe for isolating and detecting the DNA or RNA encoding a protein of the invention, or as a primer for amplifying a polynucleotide. When used as a primer, the DNA usually comprises 15-100 bp, and preferably, 15-35 bp. When used as a probe, the DNA comprises the entire sequence of a DNA of the invention, or at least a part of it, and comprises at least 15 bp. When used as a primer, the 3′-region of the polynucletide must be complementary, but the 5′-terminal may contain additional sequences, such as a restriction enzyme recognition site or a tag.

The polynucleotides of the present invention can be used for testing or diagnosing aberrations in the proteins of the present invention. For example, the polynucleotides of the present invention can be used as probes or primers to test aberrations in gene expression by Northern hybridization or RT-PCR. As used herein, the term “expression” includes transcription and/or translation. Expression analysis of the polynucleotides of the present invention may allow the testing and diagnosing of gene expression at the transcriptional level. Gene expression at the translational level may be tested or diagnosed by using antibodies raised against the proteins of the present invention as described below. Polymerase chain reaction (PCR) using as a primer a polynucleotide of the present invention, such as genomic DNA-PCR and RT-PCR, can amplify a polynucleotide encoding a protein of the present invention or an expression regulatory region. Sequence aberrations can be tested or diagnosed using RFLP analysis, SSCP, sequencing, and such.

Moreover, “a polynucleotide comprising at least 15 nucleotides, which is complementary to any of the polynucleotide sequences as set forth in SEQ ID NO. 1, 3, 5, 7 and 9, or to a complementary strand thereof” include antisense polynucleotides for inhibiting the expression of the proteins of the present invention. Antisense polynucleotides comprise at least 15 bp or more, preferably 100 bp or more, more preferably 500 bp or more, and usually 3000 bp or less, preferably 2000 bp or less.

Such antisense polynucleotides are expected to be applied in gene therapy for diseases caused by aberrations (in function or expression) in the proteins of the present invention. Specifically, in Alzheimer's disease, the aggregation and deposition of amyloid-5 protein trigger the disease and lead to the cell death of cranial nerve cells and neural dysfunctions. Therefore, if the expression of a protein of the present invention that promotes amyloid-5 protein aggregation can be inhibited, it may be useful in the treatment or prevention of Alzheimer's disease. In addition, an Alzheimer's disease model system can be produced if the expression of a protein of the present invention that suppresses amyloid-β protein aggregation can be inhibited, which will result in the promotion of amyloid-β protein aggregation. An antisense polynucleotide can be prepared, for example, by utilizing the phosphorothioate method based on the sequence information of a polynucleotide sequence shown in SEQ ID NO. 1, 3, 5, 7 or 9 (“Physicochemical properties of phosphorothioate oligodeoxynucleotides.” Stein (1988) Nucleic Acids Res. 16: 3209-3221).

A polynucleotide or antisense polynucleotide of the present invention can be used in gene therapy, for example, by administrating it to a patient by utilizing the in vivo or ex vivo method using vectors such as retrovirus vectors, adenovirus vectors, and adeno-associating virus vectors, or non-virus vectors such as liposomes.

The present invention also relates to an antibody capable of binding to a protein of the invention. The form of the antibody is not especially restricted; it includes polyclonal antibodies, monoclonal antibodies, or portions thereof, which are capable of binding to an antigen. It also includes antibodies of all classes. Furthermore, specialized antibodies such as humanized antibodies are also included.

If the antibody is a polyclonal antibody, it can be obtained according to the standard method by synthesizing a protein of this invention, or a partial peptide thereof, and immunizing rabbits with the protein or peptide (Current Protocols in Molecular Biology (1987) Ausubel et al. edit, John Wily & Sons, Section 11.12-11.13). If the antibody is a monoclonal antibody, it can be obtained by immunizing mice with a protein of this invention, or a partial peptide thereof, and producing a hybridoma cells by fusing spleen cells and myeloma cells (Current Protocols in Molecular Biology (1987) Ausubel et al. edit, John Wily & Sons, Section 11.4-11.11).

An antibody capable of binding to a protein of the present invention can be used for purifying a protein of the invention, and also for detecting and/or diagnosing aberrations in the expression and the structure of the protein. Specifically, proteins may be extracted from tissues, blood, or cells, and methods such as western blotting, immunoprecipitation, or ELISA can be used for the above purpose.

Furthermore, an antibody capable of binding to the proteins of the present invention may be utilized for treating diseases associated with the protein. If the antibody is used for treating patients, a human antibody or humanized antibody is desirable in terms of their low antigenicity. Human antibodies can be prepared by immunizing a mouse in which the immune system has been replaced with that of a human (“Functional transplant of megabase human immunoglobulin loci recapitulates human antibody response in mice” Mendez M. J. et al. (1997) Nat. Genet. 15: 146-156, for a reference) Humanized antibodies can be prepared by recombination of the hyper variable region of a monoclonal antibody (Methods in Enzymology (1991) 203: 99-121).

Among the proteins of the present invention, the proteins encoded by the polynucleotides of SEQ ID NOs. 1, 3 and 7 have an inhibitory activity on amyloid-β protein aggregation, and as shown in the Examples below, their expression decreases in patients with Alzheimer's disease. Therefore, augmentation of the expression level of these proteins will prevent amyloid-β protein aggregation, and will be useful for the treatment and prevention of Alzheimer's disease. Additionally, these proteins, and their functional equivalents, can themselves be used as therapeutic and preventive agents for Alzheimer's disease.

Among the proteins of the present invention, the proteins encoded by the polynucleotides of SEQ ID NOs. 5 and 9 have an enhancing activity on amyloid-β protein aggregation, as shown in the working examples below, and their expression increases in patients with Alzheimer's disease. Therefore, reduction of the expression level of these proteins will prevent amyloid-β protein aggregation, and will be useful for the treatment and prevention of Alzheimer's disease.

Moreover, the proteins of the present invention are expected to relate to other amyloidoses, specifically, schizophrenia and related neuropathies, rheumatoid arthritis, tuberculosis, leprosy, bronchitis, systemic lupus erythematosus (SLE), dialysis amyloidosis, diabetic amyloidosis, atrial amyloidosis, and such, and they can be used as therapeutic and preventive agents for these diseases, or for screening such therapeutic and preventive agents.

The present invention provides a method of screening for compounds regulating the activity of the proteins of the present invention. Since the proteins of the present invention prevent or promote amyloid-β protein aggregation, such compounds may be useful as therapeutic and preventive agents for Alzheimer's disease by regulating the expression of the gene products. This screening is conducted as follows.

A candidate compound that can prevent amyloid-β protein aggregation may be selected by contacting the candidate compound with a protein of the present invention, or cells expressing the protein, under conditions that permit amyloid-β protein aggregation.

More specifically, any of the proteins of the present invention, for example, a protein encoded by the nucleotide sequence of SEQ ID NO. 1, 3, 5, 7 or 9, or a protein functionally equivalent to the protein, or a cell expressing the protein, is incubated with a candidate compound in a solution containing amyloid-β protein (Aβ40, Aβ42, Aβ28, etc.). Subsequently, to determine the degree of aggregation, fluorescence intensity is measured using a fluorescent dye such as thioflavin-T, which binds to, for example, aggregated amyloid-β protein.

Among the proteins of the present invention, the increase of the expression of a protein encoded by a polynucleotide as set forth in SEQ ID NOs. 1, 3 or 7 would inhibit amyloid-β protein aggregation and thus be useful for the treatment and prevention of Alzheimer's disease. A reduction of the expression of a protein encoded by a polynucleotide as set froth in SEQ ID NOs. 5 or 9 would prevent amyloid-β protein aggregation, and thus is useful for the treatment and prevention of Alzheimer's disease. Therefore, compounds that can regulate the expression of the genes encoding the proteins of the present invention are useful as therapeutic and preventive agents. Thus, the present invention relates to a method of screening for a compound that can regulate the expression of a protein encoded by a polynucleotide of the present invention, which method comprises the following steps of:

-   -   (1) contacting a candidate compound with a cell, wherein a         vector has been introduced into said cell, said vector         comprising:         -   an expression regulatory region of a gene comprising a             nucleotide sequence selected from the group consisting of             SEQ ID NO. 1, and, a reporter gene operably linked             downstream of the expression regulatory region,     -   (2) measuring the activity of the reporter gene, and,     -   (3) selecting the candidate compound that increases or decreases         the reporter activity measured in step (2) when compared to the         control.

To carry out the screening method of the present invention, a regulatory region of the gene is isolated from chromosomal DNA, and an expression plasmid is prepared in which a reporter gene (e.g. luciferase, β-galactosidase, GFP (green fluorescent protein), etc.) is linked downstream of the regulatory region. A regulatory region that controls expression of a gene comprising a nucleotide sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, and SEQ ID NO. 9 may be cloned from chromosomal DNA by any method well known in the art. For example, S1 mapping is well known as a method for specifying transcription initiation sites (“Isolation of Transcriptional Regulatory Region” and “Isolation and Purification of Transcription Factors” in Department Oncology, The Institute of Medical Science (ed.), “Current Protocols for Cellular Engineering”, Cell Technology, Separate Volume 8, pp. 362-374, Shujunsha Co. Ltd., 1993). In general, screening of a human genomic library using a 15-100 bp, preferably 30-50 bp fragment at the 5′ terminus of the gene may allow cloning of the DNA for the regulatory region controlling gene expression as a cloned gene comprising the expression regulatory region. The cloned DNA thus obtained often contains 10 kb or longer sequence of the 5′-untranslated region of the gene. Then, the 5′-terminal region of the cloned DNA is shortened or fragmented by treating with, for example, an exonuclease. The minimal unit essential for maintaining the activity of the regulatory region can be found by evaluating the expression level or regulation of expression of the reporter gene using a sequence comprising a shortened expression regulatory region (deletion study). A computer program that predicts expression-regulatory regions of genes using Neural Network is widely known (http://www.fruitfly.org/seq_tools/promoter.html, Reese, M. G., et al, “Large Scale Sequencing Specific Neural Networks for Promoter and Splice Site Recognition” Biocomputing: Proceedings of the 1996 Pacific Symposium, edited by Lawrence Hunter and Terri E. Klein World Scientific Publishing Co, Singapore, Jan. 2-7, 1996). Alternatively, the minimal unit essential for maintaining the activity is predicted using a program such as the Promoter Scan program that searches for a transcription factor binding sequence and predicts the expression regulatory region (http://biosci.cbs.umn.edu/software/proscan/promoterscan.htm, Prestridge, D. S. 1995, Prediction of Pol II Promoter Sequence using Transcription Factor Binding Sites. J. Mol. Biol. 249: 923-932). The deletion study can be conducted, focusing on the core regions predicted.

An expression plasmid in which a reporter gene is operably linked downstream of the thus isolated gene for the regulatory region is constructed and introduced into an appropriate cell. As used herein, the term “operably linked” means that the two elements are linked so that transcription of the reporter gene is initiated by activation of the above expression regulatory region. Any gene may be used as a reporter gene as long as it encodes a protein that allows one to observe an activation of the above regulatory region as an expression of the gene. Particularly, genes such as luciferase, β-galactosidase, GFP (Green Fluorescent Protein) are typically used as reporter genes. Mammalian cells having a deletion in the corresponding gene, for example, can be used as cells for introducing the vector. Next, mammalian cells having a deletion in the corresponding gene, for example, are transfected with the expression plasmid. Expression of the reporter gene resulting from transcriptional activation by the regulatory region may be detected as a color development, luminescence, and so on. Under these conditions, this cell strain is seeded into a 96-well multiplate and compounds to be screened are added to each well, thereby allowing easy selection of compounds that can prevent or promote the expression of gene products. As a method for selecting a compound, if GFP is used as the reporter gene, the fluorescence intensities between the presence and absence of the compound can be compared. Comparison refers to when the luminescence ration is two-folds or higher, or ½ or lower, preferably five-folds or higher, or ⅕ or lower, and more preferably 10-folds or higher, or 1/10 or lower. This method can be applied to not only animal cells, but also other cells, regardless of being of eukaryotic or prokaryotic origin, as long as they can express a reporter gene in a similar system.

Test samples used in the screening include, for example, cell extracts, expression products of a gene library, synthetic low molecular weight compounds, synthetic peptides, naturally occurring compounds, etc. Note that these test compounds are examples and the present invention is not limited thereto.

Compounds isolated by this screening are candidates for a compound that promotes or suppresses the activity of a protein of the present invention (agonist or antagonist). They are also candidates as compounds that inhibit the interaction between the proteins of the present invention and certain molecules that interact with the proteins. These compounds may be possibly applied to the treatment or prevention of diseases related to the proteins of the present invention.

Further, the present invention relates to use of the compounds obtainable by the screening of the present invention for medical purposes. Thus, the present invention relates to the use of an agent comprising a compound obtainable by the aforementioned screening method as a main ingredient, in the treatment and prevention of Alzheimer's disease, or in the regulation of amyloid β protein aggregation. The present invention also relates to a therapeutic and preventive agent comprising such a compound as a main ingredient. Furthermore, compounds obtained by the screening method of the present invention are expected to be related to other amyloidoses, specifically, schizophrenia and related neuropathies, rheumatoid arthritis tuberculosis, leprosy, bronchitis, SLE, dialysis amyloidosis, diabetic amyloidosis, atrial amyloidosis, etc., and can be used as therapeutic and preventive agents for these diseases and for screening such therapeutic and preventive agents.

The proteins, nucleotides, antibodies of the present invention and the compounds isolated by the above screening mentioned are useful for regulating amyloid β protein aggregation. When used as pharmaceutical agents, they themselves can be used as pharmaceutical agents, or they can be formulated for use by any known pharmaceutical method. For example, the compounds can be formulated by mixing with pharmacologically acceptable carriers or vehicles, specifically, sterilized water, physiological saline, plant-oil, emulsifiers, suspending agents, and used. Methods well known to one skilled in the art may be used to administer a pharmaceutical agent to patients, for example as intra-arterial, intravenous, percutaneous injections, and so on. The dosage varies according to the body-weight and age of the patient, and also the administration method, but one skilled in the art can suitably select an appropriate dosage. If the compound can be encoded by a polynucleotide, the polynucleotide can be inserted into a vector for gene therapy to perform the therapy. The dosage and method of administration vary according to the body-weight, age, and symptoms of a patient, but one skilled in the art can select them suitably.

The proteins of the present invention are predicted to have other physiological activities, in addition to the activity of suppressing or promoting amyloid β protein aggregation. Such activities can be determined as follows: Since the proteins of the present invention are secretory or membrane proteins, and their amino acid sequences have been elucidated, it is possible to analyze whether they have other physiological activities, in addition to the activity of suppressing or promoting amyloid β protein aggregation, by expressing recombinants in appropriate expression systems, or by using antibodies that specifically recognize the proteins.

The biological activities of each protein of the present invention can be analyzed, based on, for example, “Glycobiology” M. Fukuda and A. Kobata (ed.), 1993; “Growth Factors” I. McKay and I. Leigh (ed.), 1993; and “Extracellular Matrix” M. A. Haralson and J. R. Hassell (ed.), 1995; in “The Practical Approach Series”, IRL PRESS, or “Glycoprotein Analysis in Biomedicine” Elizabeth F. Hounsell (ed.), 1993; in “Method in Molecular Biology” series, Humana Press. Alternatively, biological activities related to secretory or membrane proteins can be analyzed based on the disclosures found in “Growth and differentiation factors and their receptors”, The Japanese Biochemical Society (ed.), Shin-Seikagaku Jikken Kouza Vol. 7, Tokyo-Kagaku-Doujin Co. Ltd, 1991, and in Volume 296“Neurotransmitter Transporters”; Volume 294 “Ion Channels (Part C)”; Volume 293 “Ion Channels (Part B)”, Volume 292 “ABC Transporters”; Volume 288 “Chemokine Receptors”; Volume 287 “Chemokines”; Volume 248 “Proteolytic Enzymes”; Volume 245 “Extracellular Matrix Components”; Volume 244 “Proteolytic Enzymes”; Volume 230 “Guide to Techniques in Glycobiology”; Volume 198 “Peptide Growth Factors”; Volume 192 “Biomembranes”; Volume 191 “Biomembranes”; Volume 149 “Drug and Enzyme Targeting”, in “Methods in Enzymology”, Academic Press, and so on.

A pharmaceutical agent can be made based on functional analyses using a secretory or membrane protein.

In the case of a membrane protein, it would most likely be a protein having a function as a receptor or ligand by being expressed on the cell surface. Therefore, it is possible to reveal a new ligand-receptor relationship by screening a membrane protein of the invention based on the binding activity with a known ligand or receptor. Screening can be performed according to known methods.

For example, a screening using cells expressing a receptor proteins of the present invention can be performed as follows. Namely, it is possible to screen a receptor capable of binding to a specific protein by using the following steps of: (a) contacting a cell sample with a protein of the invention, or a partial peptide thereof, and (b) selecting a cell that binds to the protein or peptide.

This screening can be conducted, for example, as follows. First, a protein of the invention is expressed, and the recombinant protein is purified. Next, the purified protein is labeled, binding assay is performed using various cell lines or primary cultured cells, and cells that are expressing a receptor are selected (Growth and differentiation factors and their receptors, Shin-Seikagaku Jikken Kouza Vol. 7 (1991) Honjyo, Arai, Taniguchi, and Muramatsu edit, p203-236, Tokyo-Kagaku-Doujin). Protein labeling can be achieved by labeling with radioisotopes (R1) such as 1251, and by enzymes (alkaline phosphatase etc.) as well. Alternatively, a protein of the invention may be used without labeling, and then detected by using a labeled antibody against the protein. The cells that are selected by the above screening methods, which express a receptor of a protein of the invention, can be used for further screening agonists or antagonists of the receptor.

Once a receptor of a protein of the invention or the cells expressing the receptor is obtained by screening, it is possible to screen a compound that inhibits the binding between the protein and its receptor (agonists or antagonists of the receptor, for example) by utilizing the binding ability of the protein to its receptor or cells expressing the receptor.

The screening method comprises the steps of: (a) contacting a protein of the invention with its receptor or cells expressing the receptor in the presence of a test sample, (b) detecting the binding activity between the protein and its receptor or the cells expressing the receptor, and (c) selecting a compound that can reduce the binding activity compared to the activity in the absence of the sample.

Test samples that can be used in the screening include cell extracts, expression products of a gene library, synthesized low molecular compounds, synthesized peptides, and natural compounds, for example, but are not limited thereto. A compound that is isolated by the above screening using the binding ability of a protein of the invention can be also used as the test sample.

A compound isolated by the screening may be a candidate for an agonist or an antagonist of a receptor of a protein of the invention. By utilizing an assay that monitors a change in intracellular signaling such as phosphorylation, which results from the reduction of the binding between the protein and its receptor, it is possible to identify whether the obtained compound is an agonist or antagonist of the receptor. Also, the compound may be a candidate for a molecule that can inhibit the interaction between a protein of the invention and its associating proteins (including receptors). Such compounds can be used for developing drugs for preventing or treating a disease associated with the protein of the invention.

When a protein of the invention is a secretory protein, it may be a factor that can regulate cellular conditions such as growth and differentiation. A novel factor that regulates cellular conditions can be discovered by adding the secretory protein of the invention to a certain kind of cell, and performing screening by utilizing a cellular change in growth or differentiation, or activation of a particular gene.

The screening may be performed, for example, as follows. First, the protein of the invention is expressed and the recombinant protein is purified. Then, the purified protein is added to various kinds of cell lines or primary cultures, and a change in the cell growth and/or differentiation is monitored. Alternatively, the induction of a particular gene that is known to be involved in a certain cellular change can be detected at the level of mRNA expression or protein amount. Alternatively, the amount of an intracellular molecule (low molecular compounds) that is changed by the function of a gene product (protein) that is known to be functioning in a certain cellular change may be used for the detection.

Once the screening reveals that a protein of the invention can regulate cellular conditions or functions, it is possible to apply the protein as a pharmaceutical agent for related diseases by itself or by altering a part of it.

As was described for membrane proteins, secretory proteins provided by the invention may be used to explore a novel ligand-receptor interaction using a screening based on the binding ability to a known ligand or receptor. A similar method can be used to identify an agonist or antagonist. The resulting compounds obtained by the methods can be candidates for compounds that can inhibit the interaction between a protein of the invention and an interacting molecule (including receptors). Such compounds may used as pharmaceutical agents for preventing and treating diseases, in which the protein may play a certain role.

If a protein or gene that is affected by the screening turns out to be associated with a disease, it is possible to screen a gene or compound that can regulate its expression and/or activity either directly or indirectly by utilizing a protein of the present invention.

For example, a protein of the invention is expressed and purified as a recombinant protein. Then, the protein or gene that is affected by the screening is purified, and screened by the binding ability. Alternatively, the screening can be performed by adding in advance a compound that is a candidate for an inhibitor, and observing changes in binding. Compounds obtained by such a screening can be used for developing pharmaceutical agents for diseases with which a proteins of the present invention is associated. Similarly, if a regulatory factor obtained by the screening turns out to be a protein, a compound that affects the original expression level and/or activity of the protein can be used for the same purpose described above.

If a secretory or membrane proteins of the present invention has an enzymatic activity, it is possible to identify the activity by adding a compound to the protein under appropriate conditions, and monitoring a change of the compound. It is also possible to screen a compound that inhibits an activity of a protein of the invention by utilizing the activity as an index.

In a screening given as an example, a protein of the invention is expressed and the recombinant protein is purified. Then, a compound is added to the purified protein, and the amount of the compound and the reaction products are examined. Alternatively, a compound that is a candidate for an inhibitor is pretreated, then the compound (substrate) that can react with the purified protein is added, and the amount of the substrate and the reaction products are examined.

The compounds obtained in the screening may be used as pharmaceutical agents for diseases with which a protein of the invention is associated.

Whether or not the secretory or membrane proteins of the present invention is a novel protein associated with a disease is determined using also methods other than those described above. Namely, this can be done by obtaining a specific antibody against a protein of the invention, and examining the relationship between the expression or activity of the protein and a certain disease. In an alternative way, it may be analyzed referring to methods in “Molecular Diagnosis of Genetic Diseases” (Elles R. edit, (1996) in the series of “Method in Molecular Biology” (Humana Press).

In addition to purifying a protein of the invention, an antibody that binds to a protein of the invention may be used, for example, for testing or diagnosing structural or functional aberrations of the protein of the present invention.

Polynucleotides of the present invention were observed to be aberrantly expressed in the hippocampus of patients with Alzheimer's disease. Therefore, Alzheimer's disease may be detected by measuring the expression of a polynucleotide of the present invention. Thus, the present invention relates to a method for detecting Alzheimer's disease, comprising the following steps of:

-   -   (1) measuring the expression of at least one of the         polynucleotides selected from the group consisting of SEQ ID NO.         1, SEQ ID NO. 3, SEQ ID NO. 3, SEQ ID NO. 7, and SEQ ID NO. 9,     -   (2) comparing the measurement obtained with that obtained when         the polynucleotide is expressed in healthy subjects; and,     -   (3) linking Alzheimer's disease with said change in expression         of the polynucleotide.

In the present invention, an expression state of a polynucleotide can be understood by analyzing any one of the steps in the transcription of the gene into mRNA and in the translation into the protein. More specifically, the state of transcription can be understood by measuring mRNA comprising an aforementioned nucleotide sequence in place of an aforementioned polynucleotide. Any known method, such as Northern hybridization and RT-PCR, can be used to measure mRNA. Alternatively, measurement of a protein having an amino acid sequence encoded by a polynucleotide, or a fragment of the protein, would elucidate the state of translation into the protein. Proteins can be measured by Western blot using antibodies recognizing the proteins and various immunoassays. The testing method of the present invention can be conducted for blood samples and spinal fluid samples, or hippocampal tissue obtained by an autopsy. To observe the state of expression of the polynucleotides of the present invention, using tissue specimens as samples, analytical methods, such as in situ hybridization and immunohistological techniques, may be used. if the state of expression of a polynucleotide of the present invention is analyzed, and if, for example, the expression of PSEC256 is found to be enhanced in the brain of AD patients compared to the expression in normal brains, PSEC256 can be linked to Alzheimer's disease. Also, if inhibition of the expression of PSEC0012, PSEC0220, PSEC0242, or such, is observed, they can also be linked to Alzheimer's disease.

The present invention also relates to a reagent for revealing an expression state of a polynucleotide of the present invention. More specifically, the present invention relates to the use of a polynucleotide comprising at least 15 nucleotides, which is complementary to any one of the polynucleotides of the present invention, or to a complementary strand thereof, for detecting a polynucleotide of the present invention. Alternatively, the present invention relates to the use of an antibody recognizing any one of the proteins of the present invention for detecting the protein.

BEST MODE FOR IMPLEMENTING THE INVENTION

The present invention shall be described in detail below with reference to examples, but it is not be construed as being limited thereto.

EXAMPLE 1

Cloning of cDNAs that Encode the Proteins Promoting or Preventing Aggregation and Deposition of Amyloid β Protein

NT-2 neuron progenitor cells (Stratagene) a teratocarcinoma cell line from human embryo testis, which can differentiate into neurons when treated with retinoic acid, were used. The NT-2 cells were cultured according to the manufacturer's instructions,

-   -   (1) without retinoic acid treatment (NT2RM 1),     -   (2) 2 weeks after retinoic acid was added to cultured NT-2 cells         (NT2RP3)

The cells were harvested separately, from which mRNA was extracted by the method described in the literature (Molecular Cloning 2nd edition. Sambrook J., Fritsch, E. F., and Maniatis T. (1989) Cold Spring Harbor Laboratory Press). Poly(A)⁺RNA was further purified from the mRNA using oligo-dT cellulose.

Similarly, human placenta (PLACE1), and brain-enriched tissues from human embryo (HEMBA1) were used to extract mRNA by the method described in the literature (Molecular Cloning 2nd edition. Sambrook J., Fritsch, E. F., and Maniatis T. (1989) Cold Spring Harbor Laboratory Press). Poly(A)⁺RNA was further purified from the mRNA using oligo-dT cellulose.

Each poly(A)⁺RNA was used to construct a cDNA library by the oligo-capping method (Maruyama M. and Sugano S. (1994) Gene 138: 171-174). Using the Oligo-cap linker (agcaucgagu cggccuuguu ggccuacugg/SEQ ID NO: 11) and the Oligo-dT primer (gcggctgaag acggcctatg tggccttttt tttttttttt tt/SEQ ID NO: 12), BAP (Bacterial Alkaline Phosphatase) treatment, TAP (Tobacco Acid Phosphatase) treatment, RNA ligation, the first strand cDNA synthesis, and removal of RNA were performed as described in the reference (Suzuki and Kanno (1996) Protein Nucleic acid and Enzyme. 41: 197-201; Suzuki Y. et al. (1997) Gene 200: 149-156). Next, 5′- and 3′-PCR primers ((agcatcgagt cggccttgtt g/SEQ ID NO: 13) and (gcggctgaag acggcctatg t/SEQ ID NO: 14) respectively) were used to perform PCR (polymerase chain reaction) to convert the cDNA into double stranded cDNA, which was then digested with SfiI. Then, the DraIII-cut pUC19FL3 vector (for NT2RM1), or pME18SFL3 (GenBank AB009864, expression vector; for NT2RP3, PLACE1, and HEMBA1) was used for cloning the cDNA in an unidirectional manner, and cDNA libraries were obtained. The clones having an insert cDNA of 1 kb length or shorter were removed for NT2RM1, PLACE1, and HEMBA1, and the clones having an insert of 2 kb or shorter were removed for NT2RP3. Then, the nucleotide sequence of the 5′- and 3′-ends of the cDNA clones was analyzed using DNA sequencing reagents (Dye Terminator Cycle Sequencing FS Ready Reaction Kit, dRhodamine Terminator Cycle Sequencing FS Ready Reaction Kit, or BigDye Terminator Cycle Sequencing FS Ready Reaction Kit, from by PE Biosystems), performing sequencing reactions according to the instructions, and analyzing with a DNA sequencer (ABI PRISM 377, PE Biosystems).

The pME18SFL3 eukaryotic expression vector was used for the construction of the cDNA libraries, except for NT2RM1. The vector contains SRα promoter and SV40 small t intron in the upstream of the cloning site, and SV40 polyA added signal sequence site in the downstream. As the cloning site has asymmetrical DraIII sites, and cDNA fragments contain a complementary SfiI site on their ends, the cloned cDNA fragments can be inserted downstream of the SRα promoter unidirectionally. Therefore, the plasmid clones containing full-length cDNA can be introduced directly into COS cells to be expressed transiently. Thus, experimental analysis as proteins (gene products) or as biological activities can be very easily carried out.

The fullness ratio of the 5′-end sequence of the cDNA clones in the libraries constructed by the oligo-capping method was determined as follows. For all the clones in which the 5′-end sequence was identical to that of any known human mRNA in the public database, the clones were judged to be “complete/full length”, if they had a longer 5′-end sequences than the known human mRNA, or, even if the 5′-end sequence was shorter, if they contained a translation initiation codon. A clone that did not contain a translation initiation codon was judged to be “incomplete/not full length”. The fullness ratio ((the number of complete clones)/(the number of complete clones)+(the number of incomplete clones)) of the 5′-end of the cDNA clones from each library was determined by comparing with the known human mRNA (NT2RM1: 69%; NT2RP3: 61%; PLACE1: 68%; HEMBA1: 53%). The result indicates that the fullness ratio of the 5′-end sequence was extremely high.

The relationship between the cDNA libraries and the clones is shown below.

-   HEMBA1: PSECO220 -   NT2RM1: PSEC0012 -   NT2RP3: PSEC0242, PSEC0256 -   PLACE1: PSECO129

Furthermore the complete cDNA sequence and the predicted amino acid sequence of the clones thus selected were determined. The final nucleotide sequences were determined by combining the following three methods, and overlapping the nucleotide sequences determined by each method.

(1) Long read sequencing from both ends of the cDNA inserts using a Licor DNA sequencer (Sequence reactions were performed according to the manual of the Licor sequencer (Aloka), and DNA sequence was determined using the sequencer.)

-   -   (2) Nested sequencing by the Primer Island method which utilizes         the in vitro integration reaction of AT2 transposon (Devine S.         E., and Boeke J. D. (1994) Nucleic Acids Res. 22: 3765-3772)         (Clones were obtained using a kit from PE Biosystems, and         sequence reactions were performed using the DNA sequencing         reagents from the same company, according to the manufacturer's         instructions, and DNA sequence was determined using an ABI PRISM         377 sequencer).

(3) Primer walking by the dideoxy terminator method using custom synthesized DNA primers (Sequencing reactions were performed using the DNA sequencing reagents from PE Biosystems and custom synthesized DNA primers according to the manufacturer's instructions. DNA sequence was determined using an ABI PRISM 377 sequencer).

Obtained sequences were subjected to analysis by ATGpr [A. A. Salamov, T. NISHIKAWA, M. B. Swindells, Bioinformatics, 14: 384-390 (1998); http://www.hri.co.jp/atgpr/] and PSORT, and also to BLAST search of GenBank and SwissProt. As a result, most clones were predicted to be secretory or membrane proteins that contain a signal sequence at the N-terminus. For PSEC0242 and PSEC0256, no signal sequence was detected, but the presence of a transmembrane helix was identified by SOSUI, predicting that they are membrane proteins. The results of the above analyses suggest that PSEC0012, PSEC0129, and PSECO220 are secretory or membrane proteins and have signal sequences at their N-termini, which indicates that they are full-length cDNA clones. PSEC0242 and PSEC0256 are membrane proteins and are predicted to be full-length cDNA clones, although they lack a signal sequence. For PSEC242, a signal sequence could be found at the N-terminus, if the translation is initiated from the third ATG. PSECO242: No. 3 ATG, ATGpr1 0.82, SP-Yes, ORF 171-1343 391 aa, Signal peptide 24;

These results are shown below. The data are shown in the following order, subsequent to each clone name. Each data is discriminated by

-   “//”. -   Clone name// -   Size of cDNA// -   Number of amino acid residues composing the predicted amino acid     sequence// -   Number of ATG counted from the N-terminus// -   Maximal ATGpr1 value// -   Presence or absence of signal sequences, or prediction of signal     sequence by PSORT, prediction of membrane proteins by MEMSTAT and     SOSUI// -   Annotation: -   PSEC0012//C-NT2RM1000853//1499//183//1//0.82//125/183 (68.3%) aa     identity to fugu putative protein 2 (PUT2). -   PSEC0129//C-PLACE1004170//1828//135//1//0.94//1564/1615 (96%)     similarity to human chromosome 16q13/21 BAC clone CIT987SK-A-152E5 -   PSEC0220//C-HEMBA1005301//1584//365//1//0.94//354/365 (96%) aa     identity to mouse WNT-6 protein precursor; 1084/1310 (82%)     similarity to mouse Wnt-6 mRNA -   PSECO242//C-NT2RP3000266//3017//401//1//0.90//No & transmembrane/     /242/242 (100%) similarity to human Newcastle disease virus     inducible protein mRNA, partial 3′ UTR region; 85/341 (24%) aa     identity to human myosin heavy chain. -   PSECO256//C-NT2RP3003549//3520//612//1//0.89//No & transmembrane/     /97/362 (26%) aa identity to rat cadherin-6 precursor; 1174/1394     (84%) similarity to mRNA for KIAA0345.

Example 2 Expression of the Proteins Promoting or Preventing Amyloid β Protein Aggregation

COS cells (6×10⁶ cells/dish) were seeded, and the expression plasmids (10 μg) obtained in Example 1 were added together with 10 μl of LIPOFECTAMINE (Gibco BRL) to transfect the COS7 cells. The recombinant cells thus created, which expressed the gene of interest were cultured in D-MEM medium (+10% FCS, Pc. Sm.) for three days. Supernatant of the cultured medium was collected as a supernatant fraction.

Example 3 Amyloid β Aggregation Reaction

The supernatants obtained in Example 2 were used to screen for proteins that promote or suppress amyloid β protein aggregation. In principle, the experiments were conducted according to Methods in Enzymology Volume 309 (1999) p 274-284. Instead of Aβ40 and Aβ42, which are commonly found in vivo, Aβ1-28 consisting of 28 amino acid residues from the N-terminus of Aβ, which is considered to aggregate to a similar extent as Aβ40 and Aβ42, was used in the experiments. Experiments as shown below were conducted, and as a result, five clones showing augmented promotion or suppression of aggregation were selected from 108 clones. Experiment method and the activities of the five selected clones are shown below.

(Experiment method)

Three microliters of 1 mM Aβ1-28 (Bachem) was added to 17 μl of the culture supernatant obtained in Example 2, and the reaction was initiated by adding 10 μl of 300 mM sodium acetate buffer (pH 5.2). After 24 hours, 200 μl of 10 μM thioflavin-T (in 50 mM potassium phosphate) was added to 5 μl of the reaction sample. Aβ aggregation was determined by measuring the fluorescence intensity (excitation 450 nm, emission 482 nm). Synthesized Aβ40-1 (a peptide having the inverse sequence of Aβ40) was added to the control to a concentration of 100 μM, instead of adding the culture supernatant. The results are shown in the table below. In the table, relative fluorescence intensities are shown, when the fluorescence intensity of the Aβ1-28 aggregation resulting from the addition of Aβ40-1 is taken to be 100%. Table. 1 Changes of fluorescence intensity due to Aβ1-28 aggregates resulting from addition of Aβ40-1

Fluorescence Protein Intensity PSEC0012 (supernatant containing 24% product expressed from the clone of SEQ ID NO: 1) PSEC0129 (supernatant containing the 24% product expressed from the clone of SEQ ID NO: 3) PSEC0220 (supernatant containing the 250% product expressed from the clone of SEQ ID NO. 5) PSEC0242 (supernatant containing the 16% product expressed from the clone of SEQ ID NO. 7) PSEC0256 (supernatant containing the 460% product expressed from the clone of SEQ ID NO. 9)

The proteins expressed from the clones comprising the polynucleotides of SEQ ID NOs: 1, 3 and 7 in the sequence list prevent aggregation of amyloid βprotein, and the proteins expressed from the clones comprising the polynucleotides of SEQ ID NOs: 5 and 9 in the sequence list promote aggregation of amyloid β protein.

Furthermore, deposition of aggregated synthetic Aβ was confirmed through microscopic observation after staining with Congo red.

Example 4 Gene Expression Analysis in Patients with Alzheimer's Disease

Expression levels of the gene were compared between healthy subjects and patients with Alzheimer's disease. The primers shown below were prepared for each clone, and quantitative PCR was conducted using hippocampal cDNA as template. Hippocampal cDNA from an Alzheimer's disease patient (age 60) (NO. 0550903) and one from a healthy subject (age 28) (NO. 0510069) were purchased from BioChain Institute Inc. and used. Analysis of the expression levels was performed using PE Applied Biosystems PRISM 7700 according to the protocol for quantitative PCR using SYBR Green (P/N 4304965). The four sets of primers used for PCR are as follows:

-   PSECO12-894F: GTGGATGCGATCTGTCTCTCC (SEQ ID NO. 15) -   PSECO12-1049R: TGCAGAAAGGAACACATGCTG (SEQ ID NO. 16) -   PSEC129-190F: CTTCCATGCTTCAGCTGTGG (SEQ ID NO. 17) -   PSEC129-340R: GCCCTGGTCTGTATACCTGGG (SEQ ID NO. 18) -   PSEC242-599F: CTACGACCTGAGCCAGTGCA (SEQ ID NO. 19) -   PSEC242-749R: GAGGGCTTGGAGCTGCTGT (SEQ ID NO. 20) -   PSEC256-1502F: GCATTCTACGGGCTGGTCC (SEQ ID NO. 21) -   PSEC256-1652R: GGGTTGCCTGGTCCGTATT (SEQ ID NO. 22).

The expression level was reduced in the Alzheimer's disease patient, compared to the healthy subject, to ½ for PSEC012, 1/10 for PSEC129, and 1/9 for PSEC242. On the contrary, the expression level of PSEC256 was increased 1.5 folds in the Alzheimer's disease patient.

INDUSTRIAL APPLICABILITY

The present invention provides proteins that suppress or promote aggregation and deposition of amyloid-5 protein, and polynucleotides encoding the proteins. The proteins of the present invention and the polynucleotides encoding the proteins are useful as pharmaceutical agents for treating and preventing diseases including Alzheimer's disease, and for diagnosing these diseases. Also, the present invention has enabled screening for a compound that suppresses or promotes aggregation of amyloid-β protein. It is hoped that the screening method of the present invention would be used for developing effective therapeutic agents for Alzheimer's disease that prevent amyloid-β aggregation. 

1. An isolated polynucleotide selected from the group consisting of: (a) a polynucleotide that comprises a nucleotide sequence as set forth in SEQ ID NO:3, 5, 7 or 9, (b) a polynucleotide that encodes a polypeptide having an amino acid sequence as set forth in SEQ ID NO: 4, 6, 8 or 10, (c) a polynucleotide that hybridizes under stringent conditions to a polynucleotide comprising a nucleotide sequence as set forth in SEQ ID NO: 3, 5, 7 or 9, wherein the stringent conditions comprise washing in 0.1×SSC and 0.1% SDS at 65° C., and (d) a polynucleotide that shows at least 95% identity to a nucleotide sequence as set forth in SEQ ID NO: 3, 5, 7 or 9, or a fragment of said polynucleotide; wherein said polynucleotide or said polynucleotide fragment encodes a polypeptide (a) which suppresses or promotes the aggregation of amyloid or (b) which is an immunogenic polypeptide.
 2. The polynucleotide of claim 1 which comprises SEQ ID NO:
 3. 3. The polynucleotide of claim 1 which comprises SEQ ID NO:
 5. 4. The polynucleotide of claim 1 which comprises SEQ ID NO:
 7. 5. The polynucleotide of claim 1 which comprises SEQ ID NO:
 9. 6. The polynucleotide of claim 1 which encodes a protein having the amino acid sequence set forth in SEQ ID NO:
 4. 7. The polynucleotide of claim 1 which encodes a protein having the amino acid sequence set forth in SEQ ID NO:
 6. 8. The polynucleotide of claim 1 which encodes a protein having the amino acid sequence set forth in SEQ ID NO:
 8. 9. The polynucleotide of claim 1 encodes a protein having the amino acid sequence set forth in SEQ ID NO:
 10. 10. The polynucleotide of claim 1 which is a polynucleotide that hybridizes under stringent conditions to a polynucleotide comprising a nucleotide sequence as set forth in SEQ ID NO: 3, 5, 7 or 9, wherein the stringent conditions comprise washing in 0.1×SSC and 0.1% SDS at 65° C.
 11. The polynucleotide of claim 1 which is a polynucleotide that shows at least 95% identity to a nucleotide sequence as set forth in SEQ ID NO: 3, 5, 7 or
 9. 12. An isolated fragment of the polynucleotide of claim 1, wherein said polynucleotide fragment encodes a polypeptide (a) which suppresses or promotes the aggregation of amyloid or (b) which is an immunogenic polypeptide.
 13. The polynucleotide of claim 1 which encodes a polypeptide which suppresses the aggregation of amyloid.
 14. The polynucleotide of claim 1, which encodes a polypeptide which promotes the aggregation of amyloid.
 15. The polynucleotide of claim 1, which encodes an immunogenic polypeptide.
 16. A vector comprising the polynucleotide of claim
 1. 17. The vector of claim 15 which is an expression vector.
 18. A transfected host cell comprising the polynucleotide of claim
 1. 19. The transfected host cell of claim 18 which is a prokaryotic cell.
 20. The transfected host cell of claim 18 which is Escherichia coli.
 21. The transfected host cell of claim 18 which is a eukaryotic cell.
 22. The transfected host cell of claim 18, which is selected from the group consisting of S. cerevisiae, an HEK293 cell, a murine L929 cells, and a CHO cell.
 23. A transfected host cell comprising the vector of claim
 16. 24. A method for making a polypeptide comprising: expressing the polynucleotide of claim 1 under conditions suitable for expression of the polypeptide that it encodes, and recovering the polypeptide.
 25. A method for detecting Alzheimer's disease, comprising: (a) measuring the expression of a polynucleotide according to claim 1, (b) comparing the measurement obtained in (a) with that obtained when the polynucleotide is expressed in healthy subjects and detecting a change in expression, and (c) linking Alzheimer's disease with said change in expression of the polynucleotide.
 26. A method of screening for a compound that regulates expression of a peptide encoded by a polynucleotide according to claim 1, comprising: (a) contacting a candidate compound with a cell, wherein a vector has been introduced into said cell, said vector comprising: (i) an expression regulatory region of a gene comprising a nucleotide sequence selected from the group consisting of SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, and SEQ ID NO. 9, and, (ii) a reporter gene operably linked downstream of the expression regulatory region, (b) measuring the presence of the reporter gene, and, (c) selecting the candidate compound that increases or decreases the reporter activity measured in step (b) when compared to the control.
 27. A composition comprising the isolated polynucleotide of claim 1 and a pharmaceutically acceptable carrier or vehicle. 